When they put away childish things and read about the SOLID principles. Different time for every engineer.

SOLID is a childish thing, imo. Very undergrad.

"Single responsibility" isn't an especially useful yardstick. If you actually need to decompose a complex piece of logic into modules, the place to start is by identifying areas of high cohesion and separating them into loosely coupled functions. Ideally you can match those up to a DDD-style ubiquitous language, so your code will make intuitive sense to people familiar with the domain. "Does this have one responsibility?" really isn't the right question to ask.

The open-closed principle is straight-up wrong. Code should be easy to modify and easy to delete, and you only rarely need to add hooks for extensibility. Liskov substitution is fine, but it has more to do with correctness than cleanliness. Dependency inversion is a source of premature abstraction—you shouldn't open the door to polymorphism until you need to. Interface segregation is good, though.

In general, I think SOLID is overly enamoured with the features of object orientation. Objects themselves just aren't that big of a deal. It'd be like making the whole acronym about if-statements. If I were going to make a pithy acronym about legible code, it'd have more to say about statelessness, coupling, and unit tests. It'd reference Ousterhout's idea of deep modules, and maybe say something about "Parse, don't validate," or at least something against null values.